About This Report

PROJECTIONS

This edition of Projections of Education Statistics provides projections for key education statistics, including enrollment, graduates, teachers, and expenditures in elementary and secondary public and private schools, as well as enrollment and degrees conferred at postsecondary degree-granting institutions. Included are national data on enrollment and graduates for the past 15 years and projections to the year
2021. Also included are state-level data on enrollment in public elementary and secondary schools and public high schools from 2003, with projections to 2021. This report is organized by the level of schooling with sections 1, 2, 3, and
4 covering aspects of elementary and secondary education and sections 5 and 6 covering aspects of postsecondary education.

There are a number of limitations in projecting some
statistics. First, state-level data on enrollment and graduates in
private elementary and secondary schools and on enrollment
and degrees conferred in postsecondary degree-granting
institutions are not included. Neither the actual numbers
nor the projections of public and private elementary and
secondary school enrollment include homeschooled students
because more data are required to develop reliable projections.

Similar methodologies were used to obtain a uniform set of projections for each of the 50 states and the District
of Columbia. These projections are further adjusted to agree with the national projections of public elementary and secondary school enrollment and public high school graduates contained in this report.

The summary of projections provides highlights of the national and state data, while the reference tables and
figures present more detail. All calculations within Projections of Education Statistics are based on unrounded estimates. Therefore, the reader may find that a calculation, such as a difference or percentage change, cited in the text or figure may not be identical to the calculation obtained by using the rounded values shown in the accompanying tables.

Appendix A describes the methodology and assumptions used
to develop the projections; appendix B presents supplementary
tables; appendix C describes data sources; appendix D is a list
of the references; appendix E presents a list of abbreviations;
and appendix F is a glossary of terms.

LIMITATIONS OF PROJECTIONS

Projections of a time series usually differ from the final reported data due to errors from many sources, such as the properties of the projection methodologies, which depend on the validity of many assumptions.

The mean absolute percentage error is one way to express the forecast accuracy of past projections. This measure expresses the average of the absolute values of errors in percentage terms, where errors are the differences between past projections and actual data. For example, based on past editions of Projections of Education Statistics, the mean absolute percentage errors of public school enrollment in
grades prekindergarten-12 for lead times of 1, 2, 5, and 10 years were 0.3, 0.6, 1.3, and 2.6 percent, respectively. In contrast, mean absolute percentage errors of private school enrollment in grades prekindergarten through 8 for lead times of 1, 2, 5, and 10 years were 3.5, 4.9, 9.2, and 7.9 percent, respectively. For more information on mean absolute percentage errors, see table A-2 in appendix A.